Method and apparatus for treating hemodynamic disfunction

ABSTRACT

A method of treating hemodynamic disfunction by simultaneously pacing both ventricles of a heart. At least one ECG amplifier is arranged to separately detect contraction of each ventricle and a stimulator is then activated for issuing stimulating pulses to both ventricles in a manner to assure simultaneous contraction of both ventricles, thereby to assure hemodynamic efficiency. A first ventricle is stimulated simultaneously with contraction of a second ventricle when the first fails to properly contract. Further, both ventricles are stimulated after lapse of a predetermined A-V escape interval. One of a pair of electrodes, connected in series, in placed through the superior vena cava into the right ventricle and a second is placed in the coronary sinus about the left ventricle. Each electrode performs both pacing and sensing functions. The pacer is particularly suitable for treating bundle branch blocks or slow conduction in a portion of the ventricles.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of Reissue application No. 08/547,691, filed Oct.19, 1995 now U.S. Pat. No. RE 38,119 E, which is a continuation ofReissue application No. 07/890,280, filed May 29, 1992 now abandoned,which is a reissue of U.S. Pat. No. 4,928,688, all of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention pertains to medical devices, but more specifically, to amethod for increasing the cardiac output of a patient suffering fromcongestive heart failure by stimulating the heart of the patient atmultiple sites simultaneously.

II. Discussion of the Prior Art

Normally, impulses from the SA node affect contraction of the atria andthen propagate to the AV node. The AV node, in turn, emits a secondnerve impulse which affects contraction of the ventricles. These nerveimpulses affect contraction, i.e., depolarization of the tissue of theheart, in a coordinated manner to circulate blood through the body.Cardiac pacers of the type herein described generally are useful formaintaining proper functional operation of a sick heart. Of many cardiacdeficiencies which have in the past been diagnosed and treated,conduction difficulties have presented significant problems for which apacer has been used for treatment. A particular conduction deficiency,known as AV branch block, inhibits the transfer of nerve impulses fromthe sinoatrial (SA) node to atrial-ventricular (AV) node. When a bundleblock occurs, these nerve impulses are not properly transmitted from theSA node to the AV node and ventricles.

When this condition occurs, normal treatment is to employ a pacer whichlocks onto the rhythmic cycle of a atrial beating signal and supplies tothe ventricles a stimulating impulse at a certain time thereafter toeffect contraction of the ventricles. The time period between theoccurrence of the atrial beat and the normal contraction of theventricles is known as the A-V delay period. Generally, hemodynamicefficiency is somewhat dependent to the A-V delay period, thus the pacermust emit a stimulating pulse at a time to preserve an optimum A-V delayperiod.

Other forms of conduction deficiency, such as myocardial scarring andbundle branch block, cause slow conduction of nerve impulses, in whichcase, nerve impulses are indeed passed from the SA to the AV node, butin a time period which is slower than normal. The Q-R-S complex in thiscase would manifest itself in being very wide and hemodynamic efficiencyalso becomes lower than normal.

In each of the above-mentioned cardiac deficiencies, the heart does notcontract in coordinated fashion. This uncoordinated movement increasesdepolarization time and results in more inefficient pumping rather thana more coordinated and simultaneous ventricular depolarization. Inessence, such conduction deficiencies result in asynchrony between theleft and right ventricle.

Additionally, arrhythmias of the heart produce uncoordinated ventricularcontraction that affects the hemodynamic efficiency of the heart.Specifically, the recent paper “Incomplete Filling and IncoordinateContraction as Mechanisms of Hypotension During Ventricular Tachycardiain Man”, published in Circulation, Vol. 68, No. 5, in 1983, describesthat left ventricular function is severely disturbed by thedisorganization of wall motion in hearts undergoing ventriculartachycardias. Moreover, it was found that hearts with impaired functionsshow profound reductions in pumping ability due to incoordinatecontraction of the ventricles. It appears reasonable to believe,therefore, that any abnormal functioning heart that requires pacemakingor which has QRS widening will have a better hemodynamic efficiency ifboth ventricles are paced to contract in coordination with each other.There have been systems developed in the past employing a plurality ofelectrodes attached to the heart for effecting stimulation of aplurality of regions of the heart. For example, the Funke U.S. Pat. No.3,937,226 discloses a cardiac electrical stimulation defibrillationsystem including a plurality of electrode terminals connected in aspaced relation on the heart. The electrodes, which provide stimulatingand sensing, are each connected to amplifiers. The amplifiers areconnected to electronic control circuit means configured to causestimulation of all of the electrode terminals simultaneously in responseto a sensed depolrization signal on the heart by at least one electrodeterminal. In addition, the electronic control circuit is provided with amultivibrator means to synchronize the stimulation signal with the Q-R-Scomplex. Although Funke does teach the concept of simultaneousstimulation of a plurality of spaced electrodes, he does not discloseits specific use as a method of improving the cardiac output of patientssuffering from congestive heart failure, nor does he discuss the specficplacement of the electrodes about the heart.

The Rockland et al U.S. Pat. No. 4,088,140 discloses a similar system toFunke's although a specific use as a pacemaker is stated in the patent.Rockland, et al discloses a demand anti-arrythmia pacemaker including aplurality of sensing electrodes connected to the heart to senseventricular depolarizations. Electronic circuitry is provided having twopaths of operation. A first path provides stimulation to one area of theheart if depolarization of a naturally occurring heart beat fails tooccur within a first predetermined time period. In this first path, itis stated that the circuitry acts as a pacemaker in the event of skippednatural heartbeats. A second path provides stimulation to a plurality oflocations on the heart if a depolarization signal is sensed on the heartwithin a second predetermined time period. In this second path, it isstated that the circuitry acts as a synchronous multiple electrodepacemaker or a synchronous multiple electrode defibrillator. Although,one example of an electrode placed in the intraventricular section andothers in a spaced relation on the heart ventricles is given, there areno teachings of the specific placement of the electrodes on the heartnor the improvement of cardiac output from a sick heart. In addition,the electrodes perform either stimulating or sensing, not both,therefore a large number of electrodes is required in this system.

The Tacker, Jr. et al and McCorkle U.S. Pat. Nos. 4,548,203, 4,458,677and 4,332,259, respectively, disclose the specific placement of anelectrode in or around both left and right ventricles of the heart. TheTacker, Jr. et al patent discloses the placement of a catheter havingone electrode in the right ventricle and another outside the heart and athird electrode placed on the left ventricle. The catheter electrodes,each being paired with the left ventricular electrode, are pulsed insequence with a predetermined time separation resulting in uniformcurrent density delivered to the heart. However, this pulsing scheme andconfiguration is disclosed for use in a ventricular defibrillationdevice and not for cardiac pacing to improve cardiac output wherein amore precise synchronization of stimulation signals with the Q-R-Scomplex is required.

The McCorkle, Jr. patents disclose the specific placement of anelectrode in the right ventricle and another electrode in the coronarysinus surrounding the left ventricle for connection to a pacemaker.However, there is no specific technique disclose of providingstimulating signals to the electrodes to perform a pacemaking function.

In light of the above difficulties and shortcomings of the prior art, anobjective of the present invention is to provide a cardiac pacer forincreasing hemodynamic efficiency of a heart experiencing a conductiondeficiency.

Another objective of the invention is to ensure a more coordinated andsimultaneous ventricular depolarization of both left and rightventricles of the heart.

A yet further objective of this invention is to provide a cardiac pacersuitable for being implanted in a manner so as to impose a minimalsurgical risk during implantation thereof.

A further objective of this invention is to provide a method andapparatus of separately sensing and stimulating each ventricle of theheart in order for effecting simultaneous contraction automatically ofboth ventricles of the heart to narrow the QRS complex of a failingheart and thereby cause an increase in blood pressure and cardiacoutput.

SUMMARY OF THE INVENTION

The method of the present invention involves a procedure for pacing ofthe heart in a particular way so as to improve its contraction pattern,and thereby augment the movement of blood through the heart. Patientssuffering from severe congestive heart failure, which is found not torespond well to conventional drug therapy and to have a conductiondefect in the ventricle resulting in a widen Q-R-S complex have beenaided by a pacing regimen in which stimulating pulses are simultaneouslyapplied to both ventricles by way of a demand pacemaker or asynchronouspacemaker.

It is theorized that a considerable part of the hemodynamic impairmentin refractory congestive heart failure with conduction defects is due toan incoordinate contraction of the heart, so that a part of the heartmuscle contracts and balloons out the part that is not contracting. Whenthe latter area of the heart muscle does finally contract, the formerhas relaxed, so that a large part of the blood volume is merely shuntedback and forth within the heart rather than being ejected as wouldhappen with a more coordinate contraction pattern.

To attain the foregoing and other objectives, the present inventioncomprises, a bi-ventricular cardiac pacer having detecting andstimulating circuits for effecting substatially simultaneous contractionof both left and right ventricles of the heart. In the preferredembodiment, the bi-ventricular pacer comprises ECG amplifier means forseparately processing sensed cardiac signals from each of the right andleft ventricles. The amplified sensed signals are used to determinedwhere possible abnormal conduction delays exist on the heart and toactivate an electrical stimulator for stimulating the appropriateabnormally functioning part of the heart. More specifically, thestimulator responds to the control circuit to issue stimulating pulsessimultaneously to either the left or right ventricle, as appropriate.The stimulator may be of the demand type wherein pacing pulses are onlyissued in the absence of a normal Q-R-S complex for one or the other ofthe two ventricles (e.g., occasional bundle branch block or slowconduction), or the nondemand type wherein pacing pulses are alwaysissued (e.g., permanent bundle branch block or slow conduction).

To convey and sense signals to and from the heart, the present inventionincludes a pacing lead assembly comprising first and second separateelectrodes. The first electrode is preferably introduced through thesuperior vena cava into the right ventricle and the second electrode isintroduced through the coronary sinus to the left ventricle. Both leadsegments include a sensing and pacing tip electrode which serves to bothsense a cardiac depolarization signal or to apply a stimulating pulsefrom an implanted pulse generator to the ventricle.

Additionally, to preserve a predetermined A-V delay period, additionalatrial sensing electrodes may be placed on or around the atrial chambersof the heart and connected to the control circuit. The control circuitresponds to the sensed atrial and ventricular depolarization signals toprovide simultaneous ventricular contraction signals applied to the leftand right ventricles following a preset A-V delay period.

The advantages of the present invention include a more precise andcoordinated simultaneous ventricular depolarization of both the rightand left ventricular to thereby increase hemodynamic efficiency of apatient experiencing congestive heart failure or weak contractions.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 depicts a functional block diagram of an apparatus for carryingout the teachings of this invention; and

FIG. 2 is a logic diagram of the “CONTROL” shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates the overall pacing system which may be employed forcarrying out the teachings of the invention. A pair of leads 12 and 14with corresponding sensing/stimulating tip electrodes 13 and 15 areelectrically connected, via conductors 18 and 21, to separate ECG senseamplifiers 16 and 17 (or to a single multiplexed amplifier). Theamplifiers 16 and 17 are both connected to a control circuit unit 20. Astimulator circuit 22 is connected to the control unit 20 and has twooutput conductor lines 24 and 26 which are electrically connected to theconductors 18 and 21, respectively. From this structure, signals may beseparately sensed by the electrodes 13 and 15 and stimulating pacingsignals may be separately delivered to the electrodes 13 and 15, vialead branches 12 and 14.

In operation, the electrodes 13 and 15 are disposed in or about theright and left ventricles, respectively. A preferred surgical procedurefor-implanting the lead 12 is to extend it through the superior venacava 28 so that the sensing stimulating tip 13 thereof lodges in theinternal chamber of the right ventricle of the heart 10. A preferredsurgical-procedure for implanting lead branch 14 is to extend it throughthe coronary sinus (not shown) of the heart 10 so that thesensing/stimulating tip 15 thereof lodges directly in or about thecoronary sinus and left ventricle. Although it is described thatelectrodes 13 and 15 perform both sensing and pacing, it is possible fortesting and examination, that separate unipolar or bipolar sensing andstimulating electrodes may be used.

When attached to the heart, the electrodes 13 and 15 sense cardiacsignals in the form of well-known Q-R-S complex at separate sites withinthe left and right ventricles. The ECG amplifiers 16 and 17 feed theamplified versions of these signals to the control circuit 20.

The control circuit 20 analyzes the cardiac signals to determine whetheran abnormal conduction exists. Specifically, if a cardiac signal isreceived from the left ventricle but not from the right ventricle, thecontrol circuit 20 provides a control signal to the stimulator 22 toissue a stimulating pacing pulse over conductors 24 and 18 and leadbranch 12 to the right ventricle, via the sensing/stimulating tipelectrodes 13. Similarly, the control circuit 20 provides a controlsignal to the stimulator 22 to issue a stimulating pacing pulse overlead branch 14 to the left ventricle, via sensing/stimulating tipelectrode 15, if a cardiac depolarization signal is received from theright ventricle, but not from the left ventricle. It is also possible tosense a depolarization signal from only one ventricular chamber and thenunconditionally stimulate both ventricular chambers. This is wasteful ofpower which is a concern only if the stimulator is totally implanted andmust rely on an implanted battery power source.

The timing of the stimulating pacing pulse from the stimulator 22 issuch that both ventricles will contract substantially simultaneously.Where both ventricles are unconditionally stimulated upon the occurrenceof a QRS complex on only one side, the fact that ventricular site whichhad produced a Q-R-S complex is immediately stimulated along with theother ventricle does not cause a problem since the site producing thatcomplex is still refractory at the time it is stimulated.

It is also possible that no cardiac signals are sensed from eitherventricle, possibly resulting from complete conduction failure betweenthe sinoatrial node and the atrialventricular node. In this case, thecontrol circuit 20 will again activate the stimulator 22 to providestimulating signals to both ventricles simultaneously.

In an alternative embodiment of the invention, the issuance of pacingpulses to the ventricles is time-coupled to the rhythmic cycle of theatrial beat of the heart to preserve a preset atrial-ventricular delayperiod of about 120 to 200 milliseconds. Additional atrial sensing isaccomplished, via lead 23 and a sense electrode 25 similar to theventricular leads 12 and 14, but disposed in or about the right atrialchamber and connected to the control circuit 20, via atrial senseamplifier 27. The control circuit 20 may be configured to respond to thesensed atrial and ventricular signals to activate the stimulator forproviding appropriate simultaneous stimulating signals to the ventriclesas described above in accordance with the predetermined A-V delayperiod.

In the case where the conduction of the natural stimulating signaloriginating at the sinoatrial node of the heart 10 is only partiallyblocked or slowed, the ventricles may partially or incompletelycontract, in which case hemodynamic efficiency is reduced. Under thesecircumstances, provision is made in the control circuit 20 fordetermining whether a Q-R-S cardiac signal, although present, is weak orslow, and if so, to activate the stimulator 22 to stimulate theventricles of the heart by passing pacing pulses simultaneously thereto.

FIG. 2 shows one embodiment of the control circuitry 20 of FIG. 1required to perform bi-ventricular pacing. Also shown in the circuit ofFIG. 2 are means for interconnecting the bi-ventricular controlcircuitry with conventional demand pacing circuitry to implement variousadditional pacing modes. It is understood that in the preferredembodiment, the circuitry shown in FIG. 1 would be preferablyincorporated directly into the design of a pacer rather than itsadjunctive form shown here for purposes of illustration.

To accomplish bi-ventricular pacing, activity is sensed in both the leftand the right ventricle. When a ventricular contraction is sensed ineither ventricle, a timer is initiated. If within a time windowestablished by said timer, the contraction is sensed in the otherventricle, all pacing is inhibited because the natural contractions aredeemed to be simultaneous. On the other hand, if ventricularcontractions are not sensed in both ventricles within a period ofcoincidence defined by the time delay, at the end of this delay, thepacing pulse will be emitted, but only to the ventricle for which a QRScomplex has not been sensed. Generally, ventricular contractions whichoccur within 5-10 milliseconds of each other result in sufficienthemodynamic efficiency so as to not require treatment. Hence, the delaywindow may be of this order of magnitude. As used herein, the term“substantially simultaneous contraction” includes the occurrence ofnatural contractions of both ventricles within the window period or anevoked contraction of one or both ventricles immediately following theexpiration of the window period.

Operation of the circuit of FIG. 2 will now be described. Electricalactivity originating in the left ventricle is sensed by electrode 15 onlead 14 coupled to amplifier 16. It is assumed that amplifier 16contains all of the thresholding and inhibiting provisions commonlyutilized in existing pacing systems to inhibit all electrical activity,save valid ventricular contractions. Similarly, electrical activity inthe right ventricle is sensed by electrode 13 on lead 12 and processedby ECG amplifier 17.

Let if first be assumed that a left ventricle contraction procedes thatof the right. In this case, an R-wave signal propagates throughamplifier 16 to set the Set-Reset type flip-flop 30. a logical “1”signal passes through OR gate 32 to clock D-type of flop 34 to the “set”state which, in turn, initiates the aforementioned delay timing. Windowregister 36 is loaded with a digital count value which is representativeof the desired delay window, e.g., 5-10 ms. This may be either a fixed,hard-wired register or, alternatively, a programmable register which maybe set by telemetry means in a known manner. When the preset enableinput (PE) in high, counter 38 is held at a digital count correspondingto the value held in window register 36. When flip-flop 34 is set, thePE on counter 38 is removed, allowing the counter to be decremented witheach clock pulse provided on clock line 40. At the end of thepreprogrammed window delay interval, counter 38 is decremented to zero,causing the zero detect (ZD) line 42 to go high. The leading edge of thezero detect pulse is used to trigger a ventricle pacing pulse from pulsegenerator 44, via gates 54 and 56, as required. The pulse generatorcircuitry 44 converts this leading edge trigger to a pulse of the properamplitube and duration for effective stimulation of the right ventricle.Note that, since under the assumed conditions flip-flop 30 has been set,AND gate 48 is disabled and, therefore, pulse generator 50 is inhibitedfrom generating a left ventricle pacing pulse.

Next to be considered is the case where a right ventricle contractionhas not been sensed within the prescribed window interval. In this case,flip-flop 52 remains reset and AND gate 54 is enabled which allows thezero detect pulse ZD to propagate through OR gate 56 to trigger pulsegenerator 44, thus stimulating the right ventricle. If, however, a rightventricle contraction has been detected, flip-flop 52 would have beenset prior to the generation of the ZD pulse and, in this case, both ANDgates 48 and 54 are disabled and no pacing pulse in either ventricle isgenerated.

It can be seen from the symmetry of the circuit that the operation isidentical if the right ventricle contraction precedes the left ventriclecontraction by more than the preprogrammed delay interval. In eithercase, the setting of either flip-flop 30 or 52 causes 52 causes theinitiation of the timing window delay interval. When one of theseflip-flop sets, the other must set within the window period, otherwise apacing pulse will be generated in the unsensed ventricle.

The bi-ventriclar pacing control circuitry may be combined with otherwell-known pacer control circuitry such that the bi-ventriclar mode canbe realized in combination with any other pacing mode, such as VVI, DDD,VOO. Line 58 is the logical OR of either of left ventricle event or aright ventricle event. It may be connected to other pacing controlcircuitry 62 in place of the signal which is normally responsive to onlyactivity in the left ventricle. A sensed ventricle event thus inhibitsthe generation of a pacing trigger from another pacing circuitry andleaves the control of pacing in the alternate ventricle, as required, tothe circuitry of FIG. 1. If line 58 is not activated within the escapeinterval of the other pacing control circuitry, a paced ventricletrigger signal on line 60 is produced which propagates through both ORgate 62 and OR gate 56 to trigger pacing pulses in both ventricles.

It is also contemplated that when a ventricular depolarization signal issensed in one or the other of the ventricles, that a stimulating pulsemay also be immediately delivered, on an unconditional basis, to bothventricles, via the implanted leads 13 and 15, thus resulting in acoordinated contraction of both ventricles.

The foregoing illustrate preferred arrangements for carrying out theobjectives of this invention. Modifications and variations can obviouslybe made by those skilled in the art without departing from the truespirit and scope of the invention. For instance, the circuit may beemployed to simultaneously pace the auricles, instead of ventricles, ifsuch is required to improve pumping efficiency. The arrangement may alsobe employed as an improvement of conventional pacers thereby to improvetheir performance. As stated herein, the inventive arrangement can beused in an implanted device or in an external treating, diagnostic ortesting device. Accordingly, the invention is limited only by the scopeof the appended claims rather than by what is shown and described.Therefore, it is the intent to cover all such modifications andalternate embodiments as may come within the true scope of thisinvention.

1. A method for improving the hemodynamic efficiency of a sick heartcomprising the steps of: (a) detecting respective cardiac signalsoriginating in the left and right ventricles of the heart; (b) analyzingsaid cardiac signals and the absence thereof in an electronic controlcircuit; and (c) providing electrical pulses from a stimulating circuitcontrolled by said control circuit to one, the other or both ventriclesas required for effecting substantially simultaneous contraction of bothventricles, said step of analyzing including providing a control signalfrom said control circuit to said stimulating circuit for producing anelectrical stimulating pulse to one or both ventricles in response tothe absence of a detected cardiac signal from one or both ventricleswithin a time interval which is a small fraction of the pulse width of adetected cardiac signal.
 2. The method of claim 1 wherein said step ofdetecting respective cardiac signals comprises deposing electrodes in oron the left and right ventricles for separately detecting the respectivecardiac signals of the left and right ventricles, and applying saidcardiac signals to separate ECG amplifier means connected to each ofsaid electrodes to amplify the cardiac signal for analysis.
 3. Themethod of claim 2 wherein said step of providing electrical pulsesincludes delivering an electrical pulse from said stimulating circuit tosaid electrodes in or on both the left and right ventricles.
 4. Themethod of claim 1 wherein said step of analyzing further includesproviding a control signal from said control circuit to the stimulatingcircuit to produce an electrical stimulating pulse to the left ventriclein the absence of a detected cardiac signal from the left ventricle, orto the right ventricle in the absence of a detected cardiac signal fromthe right ventricle, or to both ventricles in the absence of detectedcardiac signals from both ventricles.
 5. A method for effectingsimultaneous contraction of both left and right ventricles of a heartfor improving hemodynamic efficiency comprising the steps of: separatelysensing for the presence of cardiac depolarization signals from bothleft and right ventricles; determining whether said cardiacdepolarization signals are simultaneously present in both the left andright ventricles; and stimulating at least one ventricle substantiallysimultaneously with the contraction of at least one other ventricle inthe event that said cardiac depolarization signals are determined not tobe simultaneously present in both ventricles.
 6. A method of effectingsimultaneous contraction of both left and right ventricles of a heartfor improving hemodynamic efficiency comprising the steps of: sensingthe cardiac signals of the atria and separately sensing the cardiacdepolarization signals of both the left and right ventricles;determining whether said cardiac depolarization signals aresimultaneously present in both the left and right ventricles;stimulating at least one ventricle simultaneously with the contractionof at least one other ventricle after a predetermined A-V period in theevent that said cardiac depolarization signals are determined not to besimultaneously present in both ventricles.
 7. A method of increasing thecardiac output of a sick heart comprising the steps of: (a) implanting apacing lead having at least two sensing/pacing electrodes in the bodysuch that one of said sensing/pacing electrodes is in or on the rightventricle and the other of said sensing/ pacing electrodes is in or onthe left ventricle; (b) sensing depolarization signals picked up by saidsensing/pacing electrodes upon their occurrence; (c) determining whetherthe depolarization signals sensed in step (b) fail to occur within apredetermined time interval of one another and, if so; (d) applying anelectrical stimulating pulse to the sensing/pacing electrode associatedwith the ventricle not producing a depolarization signal within saidtime interval at the conclusion of said time interval.
 8. The method asin claim 7 wherein said predetermined time interval is in the range offrom about 5 ms. to 10 ms.
 9. A bi-ventricular pacemaker, comprising:(a) sense means for sensing ventricular depolarization signalsoriginating in or on the right and left ventricles; (b) means coupled tosaid sense means for initiating a time delay of a predetermined lengthwhich is short compared to the period of a QRS complex upon detection ofa ventricular depolarization signal in one of said right or leftventricles; and (c) pulse generator means operative upon the terminationof said time delay for producing a ventricular simulating pulse andapplying same to the other of said right or left ventricles unless aventricular depolarization signal occurs in said other of said right ofleft ventricle prior to the expiration of said time delay.
 10. Thebi-ventricular pacemaker as in claim 9 wherein said sense meanscomprises a bi-ventricular lead having a first electrode for contactingthe right ventricle and a second electrode for contacting the leftventricle and sense amplifier means electrically coupled to said firstand second electrodes.
 11. The bi-ventricular pacemaker as in claim 10wherein said means coupled to said sense means includes: (a) first andsecond set-reset flip-flop connected to be set by an output from saidsense amplifier means; (b) presetable counter means for initiallycontaining a digital value representative of said time delay; (c) meansfor incrementing or decrementing said digital value in said presettablecounter means at regular intervals until a predetermined count isreached; (d) means responsive to the value in said counter meansreaching said predetermined count for producing a control signal; (e)logic means coupled to said first and second flip-flops and to saidpresettable counter means for receiving said control signals; andwherein (f) said pulse generator means is enabled by said logic means.12. The bi-ventricular pacemaker as in claim 11 wherein said pulsegenerator means is coupled to said first and second electrodes.
 13. Anatrial-coupled, bi-ventricular pacemaker for implantation or externaluse comprising atrial and ventricular sensing means for detectingcardiac signals, said sensing means including first and secondventricular electrodes connected in series for sensing and stimulatingthe right and the left ventricles, respectively, and an atrial electrodeadapted to be disposed in an atrial chamber for detecting cardiacsignals of the atria, all of said electrodes being connected to separateECG amplifier means for amplifying the sensed signals; a control circuitcoupled to said ECG amplifier means for analyzing the cardiac signalspicked up by said sensing means and providing a control signal; and astimulating circuit means for producing an electrical stimulating pulseto the left ventricle in the absence of a detected cardiac signal fromthe left ventricle, and to the right ventricle in the absence of adetected cardiac signal from the right ventricle, and to both ventriclesin the absence of detected cardiac signals from both ventricles toeffect substantially simultaneous contraction of both ventricles after apredetermined A-V delay period.
 14. The pacemaker of claim 13 whereinsaid first electrode is adapted to be placed in the right ventricle andthe second electrode is adapted to be placed in the coronary sinusextending about the left ventricle.
 15. A heart stimulating device fortreating heart failure, comprising: a sense amplifier to receiveventricular depolarization signals originating from a first ventricle; apulse generator, connected to the sense amplifier, to generate astimulating pulse in the event the sense amplifier receives aventricular depolarization signal; and an electrode, connected to thepulse generator, to apply the stimulating pulse to a second ventricle inthe event the sense amplifier receives a ventricular depolarizationsignal.
 16. The heart stimulating device of claim 15, the electrodefurther comprising: an electrode adapted to be disposed in or about theright ventricle to sense ventricular depolarization signals originatingfrom the right ventricle.
 17. The heart stimulating device of claim 15,wherein the sense amplifier receives ventricular depolarization signalsoriginating from the right ventricle.
 18. The heart stimulating deviceof claim 17, wherein the electrode connected to the pulse generatorapplies the stimulating pulse to the left ventricle.
 19. The heartstimulating device of claim 15, the electrode further comprising: anelectrode adapted to be disposed in or about the left ventricle to senseventricular depolarization signals originating from the left ventricle.20. The heart stimulating device of claim 15, wherein the senseamplifier receives ventricular depolarization signals originating fromthe left ventricle.
 21. The heart stimulating device of claim 20,wherein the electrode connected to the pulse generator applies thestimulating pulse to the right ventricle.
 22. The heart stimulatingdevice of claim 15, wherein the pulse generator generates thestimulating pulses immediately after the sense amplifier receives aventricular depolarization signal.
 23. The heart stimulating device ofclaim 15, further comprising: a timer to initiate a delay period afterthe sense amplifier receives a ventricular depolarization signal. 24.The heart stimulating device of claim 23, wherein the pulse generatorgenerates the stimulating pulse after the delay period.
 25. The heartstimulating device of claim 15, wherein the sense amplifier receivesventricular depolarization signals from both the right ventricle and theleft ventricle.
 26. The heart stimulating device of claim 15, whereinthe pulse generator generates stimulating pulses for both the rightventricle and the left ventricle.
 27. A heart stimulating device fortreating heart failure, comprising: means for receiving ventriculardepolarization signals originating from a first ventricle; means forgenerating a stimulating pulse in the event the receiving means receivesa ventricular depolarization signal; and means for applying thestimulating pulse to a second ventricle in the event the receiving meansreceives a ventricular depolarization signal.
 28. The heart stimulatingdevice of claim 27, the receiving means further comprising: an electrodemeans adapted to be disposed in or about the right ventricle for sensingventricular depolarization signals originating from the right ventricle.29. The heart stimulating device of claim 28, wherein the applying meansapplies the stimulating pulse to the left ventricle.
 30. The heartstimulating device of claim 28, wherein the applying means appliesstimulating pulses to both the left ventricle and the right ventricle.31. The heart stimulating device of claim 27, the receiving meansfurther comprising: an electrode means adapted to be disposed in orabout the left ventricle for sensing ventricular depolarization signalsoriginating from the left ventricle.
 32. The heart stimulating device ofclaim 31, wherein the applying means applies the stimulating pulse tothe right ventricle.
 33. The heart stimulating device of claim 31,wherein the applying means applies stimulating pulses to both the leftventricle and the right ventricle.
 34. The heart stimulating device ofclaim 27, wherein the getor means generates the stimulating pulsesimmediately after the receiving means receives a ventriculardepolarization signal.
 35. The heart stimulating device of claim 27,further comprising: means for initiating a delay period after thereceiving means receives a ventricular depolarization signal.
 36. Theheart stimulating device of claim 35, wherein the generator meansgenerates the stimulating pulse after the delay period.
 37. The heartstimulating device of claim 27, wherein the receiving means receivesventricular depolarization signals from both the right ventricle and theleft ventricle.
 38. The heart stimulating device of claim 27, whereinthe generator means generates stimulating pulses for both the rightventricle and the left ventricle.
 39. A method for improving thehemodynamic efficiency of a heart, comprising: receiving ventriculardepolarization signals originating from a first ventricle; generating astimulating pulse in response to the receiving of a ventriculardepolarization signal; and applying the stimulating pulse to a secondventricle in response to the receiving of a ventricular depolarizationsignal.
 40. The method of claim 39, the receiving further comprising:receiving ventricular depolarization signals originating from the rightventricle.
 41. The method of claim 40, the applying further comprising:applying the stimulating pulse to the left ventricle.
 42. The method ofclaim 40, the applying further comprising: applying stimulating pulsesto both the left ventricle and the right ventricle.
 43. The method ofclaim 39, the receiving further comprising: sensing ventriculardepolarization signals originating from the left ventricle.
 44. Themethod of claim 43, the applying further comprising: applying thestimulating pulse to the right ventricle.
 45. The method of claim 43,the applying further comprising: applying stimulating pulses to both theleft ventricle and the right ventricle.
 46. The method of claim 39, thegenerating further comprising: generating the stimulating pulsesimmediately after receiving a ventricular depolarization signal.
 47. Themethod of claim 39, further comprising: initiating a delay period afterreceiving a ventricular depolarization signal.
 48. The method of claim47, the generating further comprising: generating the stimulating pulseafter the delay period.
 49. The method of claim 39, the receivingfurther comprising: receiving ventricular depolarization signals fromboth the right ventricle and the left ventricle.
 50. The heartstimulating device of claim 39, the generating further comprising:generating stimulating pulses for both the right ventricle and the leftventricle.
 51. A heart stimulating device for treating heart failurecomprising: an electrode to sense a cardiac depolarization signal from afirst ventricle; a sense amplifier, connected to the electrode, toprocess the cardiac depolarization signal; and a stimulator, connectedto the sense amplifier, to issue a stimulating pulse to a secondventricle in response to the ventricular cardiac depolarization signal.52. The heart stimulating device of claim 51, wherein the electrodesenses a cardiac depolarization signal from the right ventricle.
 53. Theheart stimulating device of claim 52, wherein the stimulator issues astimulating pulse to the left ventricle in response to sensing a cardiacdepolarization signal from the right ventricle.
 54. The heartstimulating device of claim 52, wherein the stimulator issuesstimulating pulses to both ventricles in response to sensing a cardiacdepolarization signal from the right ventricle.
 55. The heartstimulating device of claim 51, wherein the electrode senses a cardiacdepolarization signal from the left ventricle.
 56. The heart stimulatingdevice of claim 55, wherein the stimulator issues a stimulating pulse tothe right ventricle in response to sensing a cardiac depolarizationsignal from the left ventricle.
 57. The heart stimulating device ofclaim 55, wherein the stimulator issues stimulating pulses to bothventricles in response to sensing a cardiac depolarization signal fromthe left ventricle.
 58. The heart stimulating device of claim 51,wherein the stimulator issues the stimulating pulse immediately afterthe electrode senses a ventricle depolarization signal.
 59. The heartstimulating device of claim 51, further comprising: a timer to initiatea delay period after the electrode senses a ventricular depolarizationsignal.
 60. The heart stimulating device of claim 59, wherein thestimulator issues the stimulating pulse after the delay period.
 61. Theheart stimulating device of claim 51, wherein the sense amplifierprocesses cardiac depolarization signals received from both the rightventricle and the left ventricle.
 62. A heart stimulating device fortreating heart failure comprising: means for sensing a cardiacdepolarization signal from a first ventricle; means, connected to thesensing means, for receiving the cardiac depolarization signal; andmeans, connected to the receiving means, for issuing a stimulating pulseto a second ventricle in response to the ventricular cardiacdepolarization signal.
 63. The heart stimulating device of claim 62,wherein the sensing means senses a cardiac depolarization signal fromthe right ventricle.
 64. The heart stimulating device of claim 63,wherein the issuing means issues a stimulating pulse to the leftventricle in response to sensing a cardiac depolarization signal fromthe right ventricle.
 65. The heart stimulating device of claim 63,wherein the issuing means issues stimulating pulses to both ventriclesin response to sensing a cardiac depolarization signal from the rightventricle.
 66. The heart stimulating device of claim 62, wherein thesensing means senses a cardiac depolarization signal from the leftventricle.
 67. The heart stimulating device of claim 66, wherein theissuing means issues a stimulating pulse to the right ventricle inresponse to sensing a cardiac depolarization signal from the leftventricle.
 68. The heart stimulating device of claim 66, wherein theissuing means issues stimulating pulses to both ventricles in responseto sensing a cardiac depolarization signal from the left ventricle. 69.The heart stimulating device of claim 62, wherein the issuing meansissues the stimulating pulse immediately after the electrode senses aventricular depolarization signal.
 70. The heart stimulating device ofclaim 62, further comprising: means for initiating a delay period afterthe electrode senses a ventricular depolarization signal.
 71. The heartstimulating device of claim 70, wherein the issuing means issues thestimulating pulse after the delay period.
 72. The heart stimulatingdevice of claim 62, wherein the receiving means receives cardiacdepolarization signals from both the right ventricle and the leftventricle.
 73. A method for improving the hemodynamic efficiency of aheart, comprising: sensing a cardiac depolarization signal from a firstventricle; receiving the ventricular cardiac depolarization signal; andissuing a stimulating pulse to a second ventricle in response to theventricular cardiac depolarization signal.
 74. The method of claim 73,the sensing further comprising: sensing a cardiac depolarization signalfrom the right ventricle.
 75. The method of claim 74, the issuingfurther comprising: issuing a stimulating pulse to the left ventricle inresponse to sensing a cardiac depolarization signal from the rightventricle.
 76. The method of claim 74, the issuing further comprising:issuing stimulating pulses to both ventricles in response to sensing acardiac depolarization signal from the right ventricle.
 77. The methodof claim 73, the sensing further comprising: sensing a cardiacdepolarization signal from the left ventricle.
 78. The method of claim77, the issuing further comprising: issuing a stimulating pulse to theright ventricle in response to sensing a cardiac depolarization signalfrom the left ventricle.
 79. The method of claim 77, the issuing furthercomprising: issuing stimulating pulses to both ventricles in response tosensing a cardiac depolarization signal from the left ventricle.
 80. Themethod of claim 73, the issuing further comprising: issuing thestimulating pulse immediately after the sensing of the ventriculardepolarization signal.
 81. The method of claim 73, further comprising:initiating a delay period after the sensing of the ventriculardepolarization signal.
 82. The method of claim 81, the issuing furthercomprising: issuing the stimulating pulse after the delay period. 83.The method of claim 73, the receiving further comprising: receivingventricular cardiac depolarization signals from both the left and theright ventricles.
 84. A heart stimulating device for treating heartfailure, comprising: an electrode to sense ventricular depolarizationsignals originating from the right ventricle; and a pulse generator,connected to the electrode, operative upon sensing of a ventriculardepolarization signal from the right ventricle to apply a stimulatingpulse to another ventricle.
 85. The heart stimulating device of claim84, wherein the pulse generator applies the stimulating pulse to theleft ventricle.
 86. The heart stimulating device of claim 84, whereinthe pulse generator applies stimulating pulses to both the leftventricle and the right ventricle.
 87. The heart stimulating device ofclaim 84, wherein the pulse generator applies the stimulating pulseimmediately upon the sensing the ventricular depolarization signal. 88.The heart stimulating device of claim 84, further comprising: a timer toinitiate a delay period after the sensing of the ventriculardepolarization signal.
 89. The heart stimulating device of claim 88,wherein the pulse generator applies the stimulating pulse after thedelay period.
 90. A heart stimulating device for treating heart failure,comprising: means for sensing ventricular depolarization signalsoriginating from the right ventricle; and means for applying astimulating pulse to another ventricle in response to the sensing meanssensing a ventricular depolarization signal originating from the rightventricle.
 91. The heart stimulating device of claim 90, wherein theapplying means applies the stimulating pulse to the left ventricle. 92.The heart stimulating device of claim 90, wherein the applying meansapplies stimulating pulses to both the left ventricle and the rightventricle.
 93. The heart stimulating device of claim 90, wherein theapplying means applies the stimulating pulse immediately upon thesensing of the ventricular depolarization signal.
 94. The heartstimulating device of claim 90, further comprising: means to initiate adelay period after the sensing of the ventricular depolarization signal.95. The heart stimulating device of claim 94, wherein the applying meansapplies the stimulating pulse after the delay period.
 96. A method forimproving the hemodynamic efficiency of a heart, comprising: sensingventricular depolarization signals originating from the right ventricle;and applying a stimulating pulse to another ventricle in response to thesensing of a ventricular depolarization signal originating from theright ventricle.
 97. The method of claim 96, the applying furthercomprising: applying the stimulating pulse to the left ventricle. 98.The method of claim 96, the applying further comprising: applyingstimulating pulses to both the left ventricle and the right ventricle.99. The method of claim 96, the applying further comprising: applyingthe stimulating pulse immediately upon the sensing of the ventriculardepolarization signal.
 100. The method of claim 96, further comprising:initiating a delay period after the sensing of the ventriculardepolarization signal.
 101. The method of claim 100, the applyingfurther comprising: applying the stimulating pulse after the delayperiod.
 102. A heart stimulating device for treating heart failure,comprising: an electrode to sense ventricular depolarization signalsoriginating from the right ventricle; and a pulse generator operativeupon sensing of a ventricular depolarization signal to apply astimulating pulse to another ventricle.
 103. The heart stimulatingdevice of claim 102, wherein the pulse generator applies the stimulatingpulse to the right ventricle.
 104. The heart stimulating device of claim102, wherein the pulse generator applies a stimulating pulse to both theright ventricle and the left ventricle.
 105. The heart stimulatingdevice of claim 102, wherein the pulse generator applies the stimulatingpulse immediately upon the sensing of the ventricular depolarizationsignal.
 106. The heart stimulating device of claim 102, furthercomprising: a timer to initiate a delay period after the sensing of theventricular depolarization signal.
 107. The heart stimulating device ofclaim 106, wherein the pulse generator applies the stimulating pulseafter the delay period.
 108. A heart stimulating device for treatingheart failure, comprising: means for sensing ventricular depolarizationsignals originating from the left ventricle; and means for applying astimulating pulse to another ventricle in response to the sensing meanssensing ventricular depolarization signals originating from the leftventricle.
 109. The heart stimulating device of claim 108, wherein theapplying means applies the stimulating pulse to the right ventricle.110. The heart stimulating device of claim 108, wherein the applyingmeans applies a stimulating pulse to both the right ventricle and theleft ventricle.
 111. The heart stimulating device of claim 108, whereinthe applying means applies the stimulating pulse immediately upon thesensing of the ventricular depolarization signal.
 112. The heartstimulating device of claim 108, further comprising: means forinitiating a delay period after the sensing of the ventriculardepolarization signal.
 113. The heart stimulating device of claim 112,wherein the applying means applies the stimulating pulse after the delayperiod.
 114. A method for improving the hemodynamic efficiency of aheart, comprising: sensing ventricular depolarization signalsoriginating from the left ventricle; and applying a stimulating pulse toanother ventricle in response to the sensing of the ventriculardepolarization signals originating from the left ventricle.
 115. Themethod of claim 114, the applying further comprising: applying thestimulating pulse to the right ventricle.
 116. The method of claim 114,the applying further comprising: applying a stimulating pulse to boththe right ventricle and the left ventricle.
 117. The method of claim114, the applying further comprising: applying the stimulating pulseimmediately upon the sensing of the ventricular depolarization signal.118. The method of claim 114, further comprising: initiating a delayperiod after the sensing of the ventricular depolarization signal. 119.The method of claim 118, the applying further comprising: applying thestimulating pulse after the delay period.
 120. A heart stimulatingdevice for treating heart failure, comprising: a first electrode tosense atrial cardiac depolarization signals originating from an atrialchamber; a second electrode to sense ventricular cardiac depolarizationsignals originating from a ventricular chamber; a pulse generatoroperative to apply stimulating pulses to both ventricles in the eventthat no ventricular cardiac depolarization signals are sensed within apredetermined atrial-ventricular delay period.
 121. The heartstimulating device of claim 120, further comprising: a control circuit,connected to the first and second electrodes, to determine whetherventricular cardiac depolarization signals are sensed by the secondelectrode within the predetermined atrial-ventricular delay period. 122.The heart stimulating device of claim 120, wherein the pulse generatorapplies the stimulating pulses to both ventricles simultaneously. 123.The heart stimulating device of claim 120, wherein the pulse generatorapplies the stimulating pulses to each of the ventricles sequentially.124. A heart stimulating device for treating heart failure, comprising:means for sensing atrial cardiac depolarization signals originating froman atrial chamber; means for sensing ventricular cardiac depolarizationsignals originating from a ventricular chamber; means for applyingstimulating pulses to both ventricles in the event that no ventricularcardiac depolarization signals are sensed within a predeterminedatrial-ventricular delay period.
 125. The heart stimulating device ofclaim 124, further comprising: a control means, connected to the atrialsensing means and the ventricular sensing means, for determining whetherventricular cardiac depolarization signals are sensed by the ventricularsensing means within the predetermined atrial-ventricular delay period.126. The heart stimulating device of claim 124, wherein the applyingmeans applies the stimulating pulses to both ventricles simultaneously.127. The heart stimulating device of claim 124, wherein the applyingmeans applies the stimulating pulses to each of the ventriclessequentially.
 128. A method for improving the hemodynamic efficiency ofa heart, comprising: sensing for the presence of cardiac depolarizationsignals from a ventricle; and stimulating both ventricles in the eventthat no cardiac depolarization signals are sensed from either ventriclewithin a predetermined atrial-ventricular delay period.
 129. The methodof claim 128, wherein stimulating both ventricles further comprisesgenerating a stimulating pulse and immediately and unconditionallyapplying the stimulating pulse to both ventricles.
 130. The method ofclaim 128, wherein stimulating both ventricles further comprisesgenerating a stimulating pulse and applying the stimulating pulse toboth ventricles simultaneously.
 131. The method of claim 128, whereinstimulating both ventricles further comprises generating a stimulatingpulse and sequentially applying the stimulating pulse to the ventricles.132. An atrial-coupled bi-ventricular stimulating device for treatmentof congestive heart failure comprising: atrial and ventricular sensingmeans for detecting cardiac signals originating in an atrium and in aventricle; a control circuit connected to said sensing means to receivethe cardiac signals and provide a control signal; and a stimulatingcircuit for effecting simultaneous contraction of both ventricles inresponse to the control signal of the control circuit after apredetermined A-V delay period.
 133. An atrial-coupled bi-ventricularstimulating device for implantation or external use for treating heartfailure comprising: a sensing electrode adapted to be located in anatrium; a pacing electrode adapted to be located through the coronarysinus in the left ventricle; a sensing electrode adapted to be locatedin the right ventricle; ventricular sensing means for detecting cardiacsignals from the sensing electrode adapted to be in the right ventricle;a control circuit connected to said sensing means to provide a controlsignal in response to detecting a cardiac signal; and a stimulatingcircuit for effecting simultaneous contraction of both ventricles inresponse to the control signal of the control circuit after apredetermined A-V delay period.
 134. The stimulating device of claim133, wherein the sensing electrode adapted to be in the right ventriclealso functions to deliver an electrical pulse from said stimulatingcircuit in response to the control signal of the control circuit. 135.The stimulating device of claim 133, wherein the pacing electrodedelivers an electrical pulse from said stimulating circuit in responseto the control signal of the control circuit.
 136. A method for treatingcongestive heart failure comprising: locating a sensing electrode in anatrium; locating a pacing electrode through the coronary sinus in theleft ventricle; locating a sensing electrode in the right ventricle;sensing for cardiac signals from the sensing electrode in the rightventricle; detecting the cardiac signals; and effecting simultaneouscontraction of both ventricles after a predetermined A-V delay period.137. The method of claim 136, wherein locating a sensing electrode inthe right ventricle includes locating a sensing and pacing electrode inthe right ventricle.
 138. The method of claim 137, wherein effectingsimultaneous contraction of both ventricles after a predetermined A-Vdelay period includes delivering an electrical pulse to the rightventricle via the sensing and pacing electrode.
 139. The method of claim136, wherein effecting simultaneous contraction of both ventricles aftera predetermined A-V delay period includes delivering an electrical pulseto the left ventricle via the pacing electrode.
 140. A method ofeffecting simultaneous contraction of both left and right ventricles ofa heart for improving hemodynamic efficiency comprising: locating apacing electrode through the coronary sinus to the left ventricle;sensing the cardiac signals of the atria and separately sensing thecardiac depolarization signals of the right ventricle; detecting thecardiac signals of the atria and the cardiac depolarization signals ofthe right ventricle; and stimulating the left ventricle simultaneouslywith the contraction of the right ventricle after a predetermined A-Vdelay period.
 141. The method of claim 140, wherein stimulating the leftventricle simultaneously with the contraction of the right ventricleafter a predetermined A-V delay period includes delivering an electricalpulse to the left ventricle via the pacing electrode.
 142. The method ofclaim 140, wherein stimulating the left ventricle simultaneously withthe contraction of the right ventricle after a predetermined A-V delayperiod includes stimulating both the left ventricle and the rightventricle after a predetermined A-V delay period.
 143. A heartstimulating device for treating heart failure, comprising: an electrodeadapted to be disposed in or about the right ventricle to senseventricular depolarization signals originating from the right ventricle;a sense amplifier to receive the ventricular depolarization signalsoriginating from the right ventricle; a pulse generator, connected tothe sense amplifier, to generate a stimulating pulse in the event thesense amplifier receives a ventricular depolarization signal originatingfrom the right ventricle; and an electrode, adapted to be disposed in orabout the left ventricle and connected to the pulse generator, to applythe stimulating pulse to the left ventricle in the event the senseamplifier receives a ventricular depolarization signal originating fromthe right ventricle.
 144. The heart stimulating device of claim 143,wherein the electrode adapted to be disposed in or about the leftventricle is positioned through the coronary sinus.
 145. The heartstimulating device of claim 143, wherein the electrode adapted to bedisposed in or about the right ventricle stimulates the right ventriclein the event the sense amplifier receives a ventricular depolarizationsignal originating from the right ventricle.
 146. A method for treatingcongestive heart failure, comprising: receiving ventriculardepolarization signals originating from the right ventricle; generatinga stimulating pulse in response to the receiving of a ventriculardepolarization signal in the right ventricle; and applying thestimulating pulse to the left ventricle in response to the receiving ofa ventricular depolarization signal in the right ventricle.
 147. Themethod of claim 146, the applying further comprising: applyingstimulating pulses to both the left ventricle and the right ventricle inresponse to the receiving of a ventricular depolarization signal in theright ventricle.
 148. The method of claim 146, further comprising:locating an electrode through the coronary sinus and in the leftventricle.
 149. A heart stimulating device for treating heart failure,comprising: an electrode adapted to be disposed in or about the leftventricle to sense ventricular depolarization signals originating fromthe left ventricle; a sense amplifier to receive the ventriculardepolarization signals originating from the left ventricle; a pulsegenerator, connected to the sense amplifier, to generate a stimulatingpulse in the event the sense amplifier receives a ventriculardepolarization signal originating from the left ventricle; and anelectrode, adapted to be disposed in or about the right ventricle andconnected to the pulse generator, to apply the stimulating pulse to theright ventricle in the event the sense amplifier receives a ventriculardepolarization signal originating from the left ventricle.
 150. Theheart stimulating device of claim 149, wherein the electrode adapted tobe disposed in or about the left ventricle is positioned through thecoronary sinus.
 151. The heart stimulating device of claim 149, whereinthe electrode adapted to be disposed in or about the left ventriclestimulates the left ventricle in the event the sense amplifier receivesa ventricular depolarization signal originating from the left ventricle.152. A method for treating a heart suffering from heart failure,comprising: receiving ventricular depolarization signals originatingfrom the left ventricle; generating a stimulating pulse in response tothe receiving of a ventricular depolarization signal in the leftventricle; and applying the stimulating pulse to the right ventricle inresponse to the receiving of a ventricular depolarization signal in theleft ventricle.
 153. The method of claim 152, the applying furthercomprising: applying stimulating pulses to both the left ventricle andthe right ventricle in response to the receiving of a ventriculardepolarization signal in the left ventricle.
 154. The method of claim152, further comprising: locating an electrode through the coronarysinus and in the left ventricle.
 155. A method for improving thehemodynamic efficiency of a heart, comprising: detecting a cardiacdepolarization signal originating from a first ventricle; andunconditionally stimulating both ventricles for effecting a coordinatedcontraction of both ventricles when a cardiac depolarization signaloriginating from the first ventricle is detected.
 156. The method ofclaim 155, wherein unconditionally stimulating both ventricles includesproviding electrical pulses from a stimulating circuit to bothventricles.
 157. The method of claim 155, wherein detecting a cardiacdepolarization signal further comprises conducting the signal to a senseamplifier to amplify the detected signal, and applying the amplifiedsignal to a control circuit.
 158. A heart stimulating device fortreating heart failure, comprising: an electrode adapted to be disposedin or about a first ventricle for detecting a cardiac depolarizationsignal originating from the first ventricle; a sense amplifier toreceive the cardiac depolarization signal originating from the firstventricle; a pulse generator, connected to the sense amplifier, tounconditionally stimulate both ventricles for effecting a coordinatedcontraction of both ventricles when the cardiac depolarization signalfrom the first ventricle is detected.
 159. The heart stimulating deviceof claim 158, further comprising an electrode adapted to be disposed inor about a second ventricle.
 160. The heart stimulating device of claim159, wherein the pulse generator unconditionally stimulates bothventricles by delivering an electronic pulse to the first ventricle viathe electrode adapted to be disposed in or about the first ventricle andby delivering an electronic pulse to the second ventricle via theelectrode adapted to be disposed in or about the second ventricle. 161.A method of improving the pumping ability of a heart suffering fromheart failure comprising: sensing for depolarization signals originatingfrom a left ventricle; sensing for depolarization signals originatingfrom a right ventricle; and stimulating the left ventricle and the rightventricle when a depolarization signal from either the left ventricle orthe right ventricle is detected for effecting a coordinate contractionof ventricles contracting in an incoordinate manner to improve thepumping ability of the heart suffering from heart failure.
 162. Themethod of claim 161, further comprising locating an electrode throughthe coronary sinus to the left ventricle.
 163. The method of claim 162,further comprising locating an electrode in the right ventricle. 164.The method of claim 161, wherein stimulating the left ventricle and theright ventricle includes stimulating the left ventricle and the rightventricle within a period of time after detecting a depolarizationsignal from either the left ventricle or the right ventricle, the periodof time being sufficient to effect a substantially simultaneouscontraction of the ventricles.
 165. The method of claim 164, wherein theleft ventricle and the right ventricle are stimulated within 10milliseconds after detecting the depolarization signal.
 166. The methodof claim 161, wherein stimulating the left ventricle and the rightventricle includes stimulating only one site in the left ventricle andonly one site in the right ventricle.
 167. The method of claim 161,wherein stimulating the left ventricle and the right ventricle includesstimulating the left ventricle and the right ventricle when adepolarization signal from either the left ventricle or the rightventricle is detected regardless of whether both ventricles wouldotherwise contract substantially simultaneously.
 168. The method ofclaim 161, wherein stimulating the left ventricle and the rightventricle includes applying a pacing pulse to the left ventricle andapplying a pacing pulse to the right ventricle.
 169. The method of claim161, wherein stimulating the left ventricle and the right ventricleincludes stimulating the left ventricle substantially simultaneouslywith stimulating the right ventricle.
 170. The method of claim 161,further comprising stimulating the left ventricle and the rightventricle if a depolarization signal from either the left ventricle orthe right ventricle is not detected within a period of time.
 171. Amethod of improving the pumping ability of a heart suffering from heartfailure comprising: sensing for depolarization signals only from oneventricle of the heart; stimulating the left ventricle and the rightventricle when a depolarization signal from the one ventricle isdetected for effecting a coordinate contraction of ventriclescontracting in an incoordinate manner to improve the pumping ability ofthe heart suffering from heart failure.
 172. The method of claim 171,further comprising locating an electrode through the coronary sinus tothe left ventricle.
 173. The method of claim 172, further comprisinglocating an electrode in the right ventricle.
 174. The method of claim171, wherein stimulating the left ventricle and the right ventricleincludes stimulating the left ventricle and the right ventricle within aperiod of time after detecting a depolarization signal from the oneventricle, the period of time being sufficient to effect a substantiallysimultaneous contraction of the ventricles.
 175. The method of claim174, wherein the left ventricle and the right ventricle are stimulatedwithin 10 milliseconds after detecting the depolarization signal. 176.The method of claim 171, wherein stimulating the left ventricle and theright ventricle includes stimulating only one site in the left ventricleand only one site in the right ventricle.
 177. The method of claim 171,wherein stimulating the left ventricle and the right ventricle includesstimulating the left ventricle and the right ventricle when adepolarization signal from the one ventricle is detected regardless ofwhether both ventricles would otherwise contract substantiallysimultaneously.
 178. The method of claim 171, wherein stimulating theleft ventricle and the right ventricle includes applying a pacing pulseto the left ventricle and applying a pacing pulse to the rightventricle.
 179. The method of claim 171, wherein stimulating the leftventricle and the right ventricle includes stimulating the leftventricle substantially simultaneously with stimulating the rightventricle.
 180. The method of claim 171, further comprising stimulatingthe left ventricle and the right ventricle if a depolarization signalfrom the one ventricle is not detected within a period of time.
 181. Themethod of claim 171, wherein the one ventricle is the right ventricle.182. The method of claim 171, wherein the one ventricle is the leftventricle.
 183. A heart failure treatment device for improving thepumping ability of a heart suffering from heart failure comprising: asense amplifier for receiving depolarization signals originating fromleft and right ventricles; and a pulse generator, connected to the senseamplifier, that generates stimulation pulses for application to the leftventricle and the right ventricle when the sense amplifier receives aventricular depolarization signal originating from either the leftventricle or the right ventricle for effecting a coordinated contractionof the ventricles to improve the pumping ability of the heart sufferingfrom heart failure; a first electrode connected to the pulse generatorand adapted to be disposed in or about the left ventricle for sensingdepolarization signals originating from the left ventricle and forapplying a stimulation pulse to the left ventricle when the senseamplifier receives a ventricular depolarization signal originating fromeither the left ventricle or the right ventricle; and a second electrodeconnected to the pulse generator and adapted to be disposed in or aboutthe right ventricle for sensing depolarization signals originating fromthe right ventricle and for applying a stimulation pulse to the rightventricle when the sense amplifier receives a ventricular depolarizationsignal originating from either the left ventricle or the rightventricle.
 184. The heart failure treatment device of claim 183, whereinthe first electrode is adapted to be positioned through the coronarysinus to the left ventricle.
 185. The heart failure treatment device ofclaim 183, wherein the stimulation pulse is applied to the leftventricle and the stimulation pulse applied to the right ventriclewithin a period of time after the sense amplifier receives adepolarization signal originating from the left ventricle or the rightventricle, the period of time being sufficient to effect substantiallysimultaneous contraction of the left and right ventricles.
 186. Theheart failure treatment device of claim 185, wherein the stimulationpulse is applied to the left ventricle and the stimulation pulse appliedto the right ventricle within 10 milliseconds after the sense amplifierreceives a depolarization signal originating from the left ventricle orthe right ventricle.
 187. The heart failure treatment device of claim183, wherein the pulse generator generates stimulation pulses forapplication to the left ventricle and the right ventricle when the senseamplifier receives a ventricular depolarization signal originating fromeither the left ventricle or the right ventricle regardless of whetherboth ventricles would otherwise contract substantially simultaneously.188. The heart failure treatment device of claim 183, wherein thestimulation pulses generated by the pulse generator are pacing pulses.189. The heart failure treatment device of claim 183, wherein thestimulation pulse applied to the left ventricle is applied substantiallysimultaneously with the stimulation pulse applied to the rightventricle.
 190. The heart failure treatment device of claim 183, whereinthe sense amplifier includes a first sense amplifier for receivingdepolarization signals originating from the right ventricle and a secondsense amplifier for receiving depolarization signals from the leftventricle.
 191. The heart failure treatment device of claim 183, whereinthe pulse generator generates stimulation pulses for application to theleft ventricle and the right ventricle if a depolarization signaloriginating from either the left ventricle or the right ventricle is notdetected within a period of time.
 192. A heart failure treatment devicefor improving the pumping ability of a heart suffering from heartfailure comprising: a sense amplifier for receiving depolarizationsignals originating from a left ventricle or a right ventricle; a pulsegenerator, connected to the sense amplifier, that generates stimulationpulses for application to the left ventricle and the right ventriclewhen the sense amplifier receives a ventricular depolarization signaloriginating from the left ventricle or the right ventricle for effectinga coordinated contraction of the ventricles to improve the pumpingability of the heart suffering from heart failure; a first electrodeconnected to the pulse generator and adapted to be disposed in or aboutthe left ventricle, the first electrode capable of sensingdepolarization signals originating from the left ventricle and capableof applying a stimulation pulse to the left ventricle when the senseamplifier receives a ventricular depolarization signal originating fromthe left ventricle or the right ventricle; and a second electrodeconnected to the pulse generator and adapted to be disposed in or aboutthe right ventricle, the second electrode capable of sensingdepolarization signals originating from the right ventricle and capableof applying a stimulation pulse to the right ventricle when the senseamplifier receives a ventricular depolarization signal originating fromthe left ventricle or the right ventricle.
 193. The heart failuretreatment device of claim 192, wherein the first electrode is adapted tobe positioned through the coronary sinus to the left ventricle.
 194. Theheart failure treatment device of claim 192, wherein the stimulationpulse is applied to the left ventricle and the stimulation pulse appliedto the right ventricle within a period of time after the sense amplifierreceives a depolarization signal originating from the left ventricle orthe right ventricle, the period of time being sufficient to effectsubstantially simultaneous contraction of the left and right ventricles.195. The heart failure treatment device of claim 194, wherein thestimulation pulse is applied to the left ventricle and the stimulationpulse applied to the right ventricle within 10 milliseconds after thesense amplifier receives a depolarization signal originating from theleft ventricle or the right ventricle.
 196. The heart failure treatmentdevice of claim 192, wherein the pulse generator generates stimulationpulses for application to the left ventricle and the right ventriclewhen the sense amplifier receives a ventricular depolarization signaloriginating from the left ventricle or the right ventricle regardless ofwhether both ventricles would otherwise contract substantiallysimultaneously.
 197. The heart failure treatment device of claim 192,wherein the stimulation pulses generated by the pulse generator arepacing pulses.
 198. The heart failure treatment device of claim 192,wherein the stimulation pulse applied to the left ventricle is appliedsubstantially simultaneously with the stimulation pulse applied to theright ventricle.
 199. The heart failure treatment device of claim 192,wherein the pulse generator generates stimulation pulses for applicationto the left ventricle and the right ventricle if a depolarization signalfrom the left ventricle or the right ventricle is not detected within aperiod of time.
 200. A heart failure treatment device for improving thepumping ability of a heart suffering from heart failure comprising: asense amplifier for receiving depolarization signals originating fromonly one ventricle of the heart; a pulse generator, connected to theamplifier for generating stimulation pulses for application to the leftventricle and the right ventricle when the sense amplifier receives aventricular depolarization signal originating from the one ventricle foreffecting a coordinated contraction of the ventricles to improve thepumping ability of the heart suffering from heart failure; a firstelectrode connected to the pulse generator and adapted to be disposed inor about the left ventricle for applying a stimulation pulse to the leftventricle when the sense amplifier receives a ventricular depolarizationsignal originating from the one ventricle; and a second electrodeconnected to the pulse generator and adapted to be disposed in or aboutthe right ventricle for applying a stimulation pulse to the rightventricle when the sense amplifier receives a ventricular depolarizationsignal originating from the one ventricle.
 201. The heart failuretreatment device of claim 200, wherein the first electrode is adapted tobe positioned through the coronary sinus to the left ventricle.
 202. Theheart failure treatment device of claim 200, wherein the stimulationpulse is applied to the left ventricle and the stimulation pulse appliedto the right ventricle within a period of time after the sense amplifierreceives a depolarization signal originating from the one ventricle, theperiod of time being sufficient to effect substantially simultaneouscontraction of the left and right ventricles.
 203. The heart failuretreatment device of claim 202, wherein the stimulation pulse is appliedto the left ventricle and the stimulation pulse applied to the rightventricle within 10 milliseconds after the sense amplifier receives adepolarization signal originating from the one ventricle.
 204. The heartfailure treatment device of claim 200, wherein the pulse generatorgenerates stimulation pulses for application to the left ventricle andthe right ventricle when the sense amplifier receives a ventriculardepolarization signal originating from the one ventricle regardless ofwhether both ventricles would otherwise contract substantiallysimultaneously.
 205. The heart failure treatment device of claim 200,wherein the stimulation pulses generated by the pulse generator arepacing pulses.
 206. The heart failure treatment device of claim 200,wherein the stimulation pulse applied to the left ventricle is appliedsubstantially simultaneously with the stimulation pulse applied to theright ventricle.
 207. The heart failure treatment device of claim 200,wherein the one ventricle is the right ventricle.
 208. The heart failuretreatment device of claim 200, wherein the one ventricle is the leftventricle.
 209. The heart failure treatment device of claim 200, whereinthe pulse generator generates stimulation pulses for application to theleft ventricle and the right ventricle if a depolarization signal fromthe one ventricle is not detected within a period of time.
 210. A methodfor improving the pumping ability of a heart suffering from heartfailure comprising: sensing for depolarization signals originating froman atrium; beginning an atrial-ventricular delay period upon sensing adepolarization signal of the atrium; sensing for depolarization signalsoriginating from a left ventricle; sensing for depolarization signalsoriginating from a right ventricle; and stimulating the left ventricleand the right ventricle at the end of the atrial-ventricular delayperiod if a depolarization signal is not detected from either the leftventricle or the right ventricle during the atrial-ventricular delayperiod for effecting a coordinated contraction of ventricles contractingin an incoordinate manner to improve the pumping ability to the heartsuffering form heart failure.
 211. The method of claim 210, furthercomprising locating an electrode through the coronary sinus to the leftventricle.
 212. The method of claim 211, further comprising locating anelectrode in the right ventricle.
 213. The method of claim 210, whereinstimulating the left ventricle and the right ventricle includesstimulating only one site in the left ventricle and only one site in theright ventricle.
 214. The method of claim 210, wherein stimulating theleft ventricle and the right ventricle includes applying a pacing pulseto the left ventricle and applying a pacing pulse to the rightventricle.
 215. The method of claim 210, wherein stimulating the leftventricle and the right ventricle includes stimulating the leftventricle substantially simultaneously with stimulating the rightventricle.
 216. A method for improving the pumping ability of a heartsuffering from heart failure comprising: sensing for depolarizationsignals originating from an atrium; beginning an atrial-ventriculardelay period upon sensing a depolarization signal of the atrium; sensingfor depolarization signals originating from only one ventricle; andstimulating the left ventricle and the right ventricle at the end of theatrial-ventricular delay period if a depolarization signal is notdetected from the one ventricle during the atrial-ventricular delayperiod for effecting a coordinated contraction of ventricles contractingin an incoordinate manner to improve the pumping ability to the heartsuffering form heart failure.
 217. The method of claim 216, furthercomprising locating an electrode through the coronary sinus to the leftventricle.
 218. The method of claim 217, further comprising locating anelectrode in the right ventricle.
 219. The method of claim 216, whereinstimulating the left ventricle and the right ventricle includesstimulating only one site in the left ventricle and only one site in theright ventricle.
 220. The method of claim 216, wherein stimulating theleft ventricle and the right ventricle includes applying a pacing pulseto the left ventricle and applying a pacing pulse to the rightventricle.
 221. The method of claim 216, wherein stimulating the leftventricle and the right ventricle includes stimulating the leftventricle substantially simultaneously with stimulating the rightventricle.
 222. The method of claim 216, wherein the one ventricle isthe right ventricle.
 223. The method of claim 216, wherein the oneventricle is the left ventricle.
 224. A heart failure treatment devicefor improving the pumping ability of a heart suffering from heartfailure comprising: an atrial sense amplifier for detectingdepolarization signals originating from an atrium; a ventricular senseamplifier for detecting depolarization signals originating from a leftventricle and a right ventricle; pacing control circuitry, connected tothe atrial sense amplifier, for starting an atrial-ventricular delayperiod when the atrial sense amplifier detects an atrial depolarizationsignal; and a stimulating circuit capable of stimulating the leftventricle and the right ventricle at the end of the atrial-ventriculardelay period if a depolarization signal is not detected from either theleft ventricle or the right ventricle during the atrial-ventriculardelay period for effecting coordinated contraction of ventriclescontracting in an incoordinate manner to improve the pumping ability tothe heart suffering form heart failure.
 225. The heart failure treatmentdevice of claim 224, further comprising an electrode adapted to bepositioned through the coronary sinus to the left ventricle forstimulating the left ventricle.
 226. The heart failure treatment deviceof claim 224, wherein the stimulating circuit generates pacing pulsesfor stimulating the left ventricle and the right ventricle.
 227. Theheart failure treatment device of claim 224, wherein the stimulationcircuit stimulates the left ventricle substantially simultaneously withstimulation of the right ventricle.
 228. The heart failure treatmentdevice of claim 224, wherein the ventricular sense amplifiers includes afirst ventricular sense amplifier connected to the pacing controlcircuitry for detecting depolarization signals originating from the leftventricle and a second ventricular sense amplifier connected to thepacing control circuitry for detecting depolarization signalsoriginating from the right ventricle.
 229. A heart failure treatmentdevice for improving the pumping ability of a heart suffering from heartfailure comprising: an atrial sense amplifier capable of detectingdepolarization signals originating from an atrium; a ventricular senseamplifier capable of detecting depolarization signals originating from aleft ventricle or a right ventricle; pacing control circuitry, connectedto the atrial sense amplifier, capable of starting an atrial-ventriculardelay period when the atrial sense amplifier detects an atrialdepolarization signal; a stimulating circuit capable of providingstimulating pulses for application to the left ventricle and the rightventricle at the end of the atrial-ventricular delay period if adepolarization signal is not detected from the left ventricle or theright ventricle during the atrial-ventricular delay period for effectingcoordinated contraction of ventricles contracting in an incoordinatemanner to improve the pumping ability to the heart suffering form heartfailure; a first electrode responsive to the stimulating circuit andadapted to be disposed in or about the left ventricle, the firstelectrode capable of sensing depolarization signals originating from theleft ventricle and capable of providing stimulating pulses to the leftventricle when the ventricular sense amplifier receives a depolarizationsignal from the left ventricle or the right ventricle; and a secondelectrode responsive to the stimulating circuit and adapted to bedisposed in or about the right ventricle, the second electrode capableof sensing depolarization signals originating from the right ventricleand capable of providing stimulating pulses to the right ventricle whenthe sense amplifier receives a depolarization signal from the leftventricle or the right ventricle.
 230. The heart failure treatmentdevice of claim 229, wherein the first electrode is adapted to bepositioned through the coronary sinus to the left ventricle.
 231. Theheart failure treatment device of claim 229, wherein the left ventricleis stimulated substantially simultaneously with stimulation of the rightventricle.
 232. A heart failure treatment device for improving thepumping ability of a heart suffering from heart failure comprising: anatrial sense amplifier for detecting depolarization signals originatingfrom an atrium; a ventricular sense amplifier for detectingdepolarization signals originating from only one ventricle; pacingcontrol circuitry, connected to the atrial sense amplifier, for startingan atrial-ventricular delay period when the atrial sense amplifierdetects an atrial depolarization signal; and a stimulating circuitcapable of stimulating the left ventricle and the right ventricle at theend of the atrial-ventricular delay if a depolarization signal is notdetected from the one ventricle during the atrial-ventricular delayperiod for effecting coordinated contraction of ventricles contractingin an incoordinate manner to improve the pumping ability to the heartsuffering form heart failure.
 233. The heart failure treatment device ofclaim 232, further comprising an electrode adapted to be positionedthrough the coronary sinus to the left ventricle for stimulating theleft ventricle.
 234. The heart failure treatment device of claim 232,wherein the stimulating circuit generates pacing pulses for stimulatingthe left ventricle and the right ventricle.
 235. The heart failuretreatment device of claim 232, wherein the stimulation circuitstimulates the left ventricle substantially simultaneously withstimulation of the right ventricle.
 236. The heart failure treatmentdevice of claim 232, wherein the one ventricle is the right ventricle.237. The heart failure treatment device of claim 232, wherein the oneventricle is the left ventricle.
 238. A method of improving the pumpingability of a heart suffering from heart failure comprising: sensing fordepolarization signals originating from an atrium; beginning anatrial-ventricular delay period upon sensing a depolarization signal ofthe atrium; sensing for depolarization signals originating from a leftventricle; sensing for depolarization signals originating from a rightventricle; and stimulating the left ventricle and the right ventriclewhen a depolarization signal from either the left ventricle or the rightventricle is detected during the atrial-ventricular delay period foreffecting a coordinated contraction of the ventricles contracting in anincoordinate manner to improve the pumping ability of the heartsuffering from heart failure; and stimulating the left ventricle and theright ventricle at the end of the atrial-ventricular delay period if adepolarization signal is not detected from either the left ventricle orthe right ventricle during the atrial-ventricular delay period foreffecting a coordinated contraction of the ventricles.
 239. The methodof claim 238, further comprising locating an electrode through thecoronary sinus to the left ventricle.
 240. The method of claim 239,further comprising locating an electrode in the right ventricle. 241.The method of claim 238, wherein the left ventricle is stimulated andthe right ventricle is stimulated within a period of time after adepolarization signal from either the left ventricle or the rightventricle is detected during the atrial-ventricular delay period, theperiod of time being sufficient for effecting substantially simultaneouscontraction of the ventricles.
 242. The method of claim 241, wherein theleft ventricle and the right ventricle are stimulated within 10milliseconds of the detection of the depolarization signal.
 243. Themethod of claim 238, wherein stimulating the left ventricle and theright ventricle includes stimulating only one site in the left ventricleand only one site in the right ventricle.
 244. The method of claim 238,wherein the left ventricle and the right ventricle are stimulated when adepolarization signal from either the left ventricle or the rightventricle is detected during the atrial-ventricular delay periodregardless of whether both ventricles would otherwise contractsubstantially simultaneously.
 245. The method of claim 238, whereinstimulating the left ventricle and the right ventricle includes applyinga pacing pulse to the left ventricle and applying a pacing pulse to theright ventricle.
 246. The method of claim 238, wherein stimulating theleft ventricle and the right ventricle includes stimulating the leftventricle substantially simultaneously with stimulating the rightventricle.
 247. A method of improving the pumping ability of a heartsuffering from heart failure comprising: sensing for depolarizationsignals originating from an atrium; beginning an atrial-ventriculardelay period upon sensing a depolarization signal of the atrium; sensingfor depolarization signals originating from only one ventricle;stimulating the left ventricle and the right ventricle when adepolarization signal from the one ventricle is detected during theatrial-ventricular delay period for effecting a coordinated contractionof the ventricles; and stimulating the left ventricle and the rightventricle at the end of the atrial-ventricular delay period if adepolarization signal is not detected from the one ventricle during theatrial-ventricular delay period for effecting a coordinated contractionof ventricles contracting in an incoordinate manner to improve thepumping ability of the heart suffering from heart failure.
 248. Themethod of claim 247, further comprising locating an electrode throughthe coronary sinus to the left ventricle.
 249. The method of claim 248,further comprising locating an electrode in the right ventricle. 250.The method of claim 247, wherein the left ventricle is stimulated andthe right ventricle is stimulated within a period of time after adepolarization signal from the one depolarization is detected during theatrial-ventricular delay period, the period of time being sufficient foreffecting substantially simultaneous contraction of the ventricles. 251.The method of claim 250, wherein the left ventricle and the rightventricle are stimulated within 10 milliseconds of the detection of thedepolarization signal.
 252. The method of claim 247, wherein stimulatingthe left ventricle and the right ventricle includes stimulating only onesite in the left ventricle and only one site in the right ventricle.253. The method of claim 247, wherein the left ventricle and the rightventricle are stimulated when a depolarization signal from the oneventricle is detected during the atrial-ventricular delay periodregardless of whether both ventricles would otherwise contractsubstantially simultaneously.
 254. The method of claim 247, whereinstimulating the left ventricle and the right ventricle includes applyinga pacing pulse to the left ventricle and applying a pacing pulse to theright ventricle.
 255. The method of claim 247, wherein stimulating theleft ventricle and the right ventricle includes stimulating the leftventricle substantially simultaneously with stimulating the rightventricle.
 256. The method of claim 247, wherein the one ventricle isthe right ventricle.
 257. The method of claim 247, wherein the oneventricle is the left ventricle.
 258. A heart failure treatment devicefor improving the pumping ability of a heart suffering from heartfailure comprising: an atrial sense amplifier for detectingdepolarization signals originating from an atrium; pacing controlcircuitry, connected to the atrial sense amplifier, for starting anatrial-ventricular delay period when the atrial sense amplifier detectsan atrial depolarization signal; a ventricular sense amplifier fordetecting depolarization signals originating from a left ventricle and aright ventricle; and a stimulating circuit for stimulating the leftventricle and the right ventricle when a depolarization signal fromeither the left or the right ventricle is detected by the ventricularsense amplifier during the atrial-ventricular delay period for effectinga coordinated contraction of ventricles contracting in an incoordinatemanner to improve the pumping ability of the heart suffering from heartfailure; and for stimulating the left ventricle and the right ventricleat the end of the atrial-ventricular delay period if a depolarizationsignal is not detected from either the left or right ventricles duringthe atrial-ventricular delay period for effecting a coordinatedcontraction of ventricles contracting in an incoordinate manner toimprove the pumping ability of the heart suffering from heart failure.259. The heart failure treatment device of claim 259, further comprisingan electrode adapted to be positioned through the coronary sinus to theleft ventricle for stimulating the left ventricle.
 260. The heartfailure treatment device of claim 258, wherein the stimulation circuitstimulates the left ventricle and the right ventricle within a timeperiod after a depolarization signal from either the left or the rightventricle is detected by the ventricular sense amplifier, the timeperiod being sufficient for effecting substantially simultaneouscontraction of the left ventricle and the right ventricle.
 261. Theheart failure treatment device of claim 260, wherein the stimulationcircuit stimulates the left ventricle and the right ventricle within 10milliseconds of the ventricular sense amplifier detecting adepolarization signal from either the left ventricle or the rightventricle.
 262. The heart failure treatment device of claim 258, whereinthe stimulating circuit stimulates the left ventricle and the rightventricle when a depolarization signal from either the left ventricle orthe right ventricle is detected by the ventricular sense amplifierduring the atrial-ventricular delay period regardless of whether bothventricles would otherwise contract substantially simultaneously. 263.The heart failure treatment device of claim 258, wherein the stimulatingcircuit generates pacing pulses for stimulating the left ventricle andthe right ventricle.
 264. The heart failure treatment device of claim258, wherein the stimulation circuit stimulates the left ventriclesubstantially simultaneously with stimulation of the right ventricle.265. The heart failure treatment device of claim 258, wherein theventricular sense amplifiers includes a first ventricular senseamplifier for detecting depolarization signals originating from the leftventricle and second ventricular sense amplifier for detectingdepolarization signals originating from the right ventricle.
 266. Aheart failure treatment device for improving the pumping ability of aheart suffering from heart failure comprising: a atrial sense amplifierfor detecting depolarization signals originating from an atrium; pacingcontrol circuitry, connected to the atrial sense amplifier, for startingan atrial-ventricular delay period when the atrial sense amplifierdetects an atrial depolarization signal; a ventricular sense amplifierfor detecting depolarization signals originating from the left ventricleor the right ventricle; a stimulating circuit for stimulating the leftventricle and the right ventricle when a depolarization signal from theleft ventricle or the right ventricle is detected by the ventricularsense amplifier during the atrial-ventricular delay period for effectinga coordinated contraction of ventricles contracting in an incoordinatemanner to improve the pumping ability of the heart suffering from heartfailure; and for stimulating the left ventricle and the right ventricleat the end of the atrial-ventricular delay period if a depolarizationsignal is not detected from the left ventricle or the right ventricleduring the atrial-ventricular delay period for effecting a coordinatedcontraction of ventricles contracting in an incoordinate manner toimprove the pumping ability of the heart suffering from heart failure; afirst electrode adapted to be disposed in or about the left ventricle,the first electrode capable of sensing depolarization signalsoriginating from the left ventricle and capable of providing astimulating pulse to the left ventricle in response to the stimulatingcircuit; and a second electrode adapted to be disposed in or about theright ventricle, the second electrode capable of sensing depolarizationsignals originating from the right ventricle and capable of providing astimulating pulse to the right ventricle in response to the stimulatingcircuit.
 267. The heart failure treatment device of claim 266, whereinthe first electrode is adapted to be positioned through the coronarysinus to the left ventricle.
 268. The heart failure treatment device ofclaim 266, wherein the stimulating circuit generates pacing pulses forstimulating the left ventricle and the right ventricle.
 269. The heartfailure treatment device of claim 266, wherein the left ventricle isstimulated substantially simultaneously with stimulation of the rightventricle.
 270. The heart failure treatment device of claim 266, whereinthe stimulation circuit stimulates the left ventricle and the rightventricle within a time period after a depolarization signal from theleft ventricle or the right ventricle is detected by the ventricularsense amplifier, the time period being sufficient for effectingsubstantially simultaneous contraction of the left ventricle and theright ventricle.
 271. The heart failure treatment device of claim 270,wherein the stimulation circuit stimulates the left ventricle and theright ventricle within 10 milliseconds of the ventricular senseamplifier detecting a depolarization signal from the left ventricle orthe right ventricle.
 272. A heart failure treatment device for improvingthe pumping ability of a heart suffering from heart failure comprising:an atrial sense amplifier for detecting depolarization signalsoriginating from an atrium; pacing control circuitry, connected to theatrial sense amplifier, for starting an atrial-ventricular delay periodwhen the atrial sense amplifier detects an atrial depolarization signal;a ventricular sense amplifier for detecting depolarization signalsoriginating from only one ventricle; and a stimulating circuit forstimulating the left ventricle and the right ventricle when adepolarization signal from the one ventricle is detected by theventricular sense amplifier during the atrial-ventricular delay periodfor effecting a coordinated contraction of ventricles contracting in anincoordinate manner to improve the pumping ability of the heartsuffering from heart failure; and for stimulating the left ventricle andthe right ventricle at the end of the atrial-ventricular delay period ifa depolarization signal is not detected from the one ventricle duringthe atrial-ventricular delay period for effecting a coordinatedcontraction of ventricles contracting in an incoordinate manner toimprove the pumping ability of the heart suffering from heart failure.273. The heart failure treatment device of claim 272, further comprisingan electrode adapted to be positioned through the coronary sinus to theleft ventricle for stimulating the left ventricle.
 274. The heartfailure treatment device of claim 272, wherein the stimulation circuitstimulates the left ventricle and the right ventricle within a timeperiod after a depolarization signal from the one ventricle is detectedby the ventricular sense amplifier, the time period being sufficient foreffecting substantially simultaneous contraction of the left ventricleand the right ventricle.
 275. The heart failure treatment device ofclaim 274, wherein the stimulation circuit stimulates the left ventricleand the right ventricle within 10 milliseconds of the ventricular senseamplifier detecting a depolarization signal from the one ventricle. 276.The heart failure treatment device of claim 272, wherein the stimulatingcircuit stimulates the left ventricle and the right ventricle when adepolarization signal from the one ventricle is detected by theventricular sense amplifier during the atrial-ventricular delay periodregardless of whether both ventricles would otherwise contractsubstantially simultaneously.
 277. The heart failure treatment device ofclaim 272, wherein the stimulating circuit generates pacing pulses forstimulating the left ventricle and the right ventricle.
 278. The heartfailure treatment device of claim 272, wherein the stimulation circuitstimulates the left ventricle substantially simultaneously with thestimulation of the right ventricle.
 279. The heart failure treatmentdevice of claim 272, wherein the one ventricle is the right ventricle.280. The heart failure treatment device of claim 272, wherein the oneventricle is the left ventricle.
 281. A method of improving the pumpingability of a heart suffering from heart failure comprising: sensing fordepolarization signals originating from an atrium; beginning anatrial-ventricular delay period upon sensing a depolarization signal ofthe atrium; sensing for depolarization signals originating from a leftventricle; sensing for depolarization signals originating from a rightventricle; inhibiting stimulation of the left ventricle and the rightventricle when a depolarization signal from either the left ventricle orthe right ventricle is detected during the atrial-ventricular delayperiod; and stimulating the left ventricle and the right ventricle atthe end of the atrial-ventricular delay period if a depolarizationsignal is not detected from either the left ventricle or the rightventricle during the atrial-ventricular delay period.
 282. The method ofclaim 281, further comprising locating an electrode through the coronarysinus to the left ventricle.
 283. The method of claim 282, furthercomprising locating an electrode in the right ventricle.
 284. The methodof claim 281, wherein stimulating the left ventricle and the rightventricle includes stimulating only one site in the left ventricle andonly one site in the right ventricle.
 285. The method of claim 281,wherein stimulating the left ventricle and the right ventricle includesapplying a pacing pulse to the left ventricle and applying a pacingpulse to the right ventricle.
 286. The method of claim 281, whereinstimulating the left ventricle and the right ventricle includesstimulating the left ventricle substantially simultaneously withstimulating the right ventricle.
 287. A method of improving the pumpingability of a heart suffering from heart failure comprising: sensing fordepolarization signals originating from an atrium; beginning anatrial-ventricular delay period upon sensing a depolarization signal ofthe atrium; sensing for depolarization signals originating from only oneventricle; inhibiting stimulation of the left ventricle and the rightventricle when a depolarization signal from the one ventricle isdetected during the atrial-ventricular delay period; and stimulating theleft ventricle and the right ventricle at the end of theatrial-ventricular delay period if a depolarization signal is notdetected from the one ventricle during the atrial-ventricular delayperiod.
 288. The method of claim 287, further comprising locating anelectrode through the coronary sinus to the left ventricle.
 289. Themethod of claim 288, further comprising locating an electrode in theright ventricle.
 290. The method of claim 287, wherein stimulating theleft ventricle and the right ventricle includes stimulating only onesite in the left ventricle and only one site in the right ventricle.291. The method of claim 287, wherein stimulating the left ventricle andthe right ventricle includes applying a pacing pulse to the leftventricle and applying a pacing pulse to the right ventricle.
 292. Themethod of claim 287, wherein stimulating the left ventricle and theright ventricle includes stimulating the left ventricle substantiallysimultaneously with stimulating the right ventricle.
 293. A heartfailure treatment device for improving the pumping ability of a heartsuffering from heart failure comprising: an atrial sense amplifier fordetecting depolarization signals originating from an atrium; aventricular sense amplifier for detecting depolarization signalsoriginating from a left ventricle and a right ventricle; pacing controlcircuitry, connected to the atrial sense amplifier, for starting anatrial-ventricular delay period when the atrial sense amplifier detectsan atrial depolarization signal, and for inhibiting stimulation of theleft ventricle and the right ventricle when a depolarization signal fromeither the left or the right ventricle is detected during theatrial-ventricular delay period; and a stimulating circuit forstimulating the left ventricle and the right ventricle at the end of theatrial-ventricular delay period if a depolarization signal is notdetected from either the left ventricle or the right ventricle duringthe atrial-ventricular delay period for effecting a coordinatedcontraction of ventricles contracting in an incoordinate manner toimprove the pumping ability of the heart suffering from heart failure.294. The heart failure treatment device of claim 293, further comprisingan electrode adapted to be positioned through the coronary sinus to theleft ventricle for stimulating the left ventricle.
 295. The heartfailure treatment device of claim 293, wherein the stimulating circuitgenerates pacing pulses for stimulating the left ventricle and the rightventricle.
 296. The heart failure treatment device of claim 293, whereinthe stimulation circuit stimulates the left ventricle substantiallysimultaneously with the stimulation of the right ventricle.
 297. Theheart failure treatment device of claim 293, wherein the ventricularsense amplifier includes a first ventricular sense amplifier forreceiving depolarization signals originating from the right ventricleand a second ventricular sense amplifier for receiving depolarizationsignals from the left ventricle.
 298. A heart failure treatment devicefor improving the pumping ability of a heart suffering from heartfailure comprising: an atrial sense amplifier for detectingdepolarization signals originating from an atrium; a ventricular senseamplifier for detecting depolarization signals originating from a leftventricle or a right ventricle; pacing control circuitry, connected tothe atrial sense amplifier, for starting an atrial-ventricular delayperiod when the atrial sense amplifier detects an atrial depolarizationsignal, and for inhibiting stimulation of the left ventricle and theright ventricle when a depolarization signal from either the left or theright ventricle is detected during the atrial-ventricular delay period;a stimulating circuit for providing stimulating pulses for applicationto the left ventricle and the right ventricle at the end of theatrial-ventricular delay period if a depolarization signal is notdetected from the left ventricle or the right ventricle during theatrial-ventricular delay period for effecting a coordinated contractionof ventricles contracting in an incoordinate manner to improve thepumping ability of the heart suffering from heart failure; a firstelectrode adapted to be disposed in or about the left ventricle, thefirst electrode capable of sensing depolarization signals originatingfrom the left ventricle and capable of providing a stimulating pulse tothe left ventricle in response to the stimulating circuit; and a secondelectrode adapted to be disposed in or about the right ventricle, thesecond electrode capable of sensing depolarization signals originatingfrom the right ventricle and capable of providing a stimulating pulse tothe right ventricle in response to the stimulating circuit.
 299. Theheart failure treatment device of claim 298, wherein the first electrodeis adapted to be positioned through the coronary sinus to the leftventricle.
 300. The heart failure treatment device of claim 298, whereinthe stimulating circuit generates pacing pulses for stimulating the leftventricle and the right ventricle.
 301. The heart failure treatmentdevice of claim 298, wherein the left ventricle is stimulatedsubstantially simultaneously with the stimulation of the rightventricle.
 302. A heart failure treatment device for improving thepumping ability of a heart suffering from heart failure comprising: anatrial sense amplifier for detecting depolarization signals originatingfrom an atrium; a ventricular sense amplifier for detectingdepolarization signals originating from only one ventricle; pacingcontrol circuitry, connected to the atrial sense amplifier, for startingan atrial-ventricular delay period when the atrial sense amplifierdetects an atrial depolarization signal, and for inhibiting stimulationof the left ventricle and the right ventricle when a depolarizationsignal from the one ventricle is detected during the atrial-ventriculardelay period; and a stimulating circuit for stimulating the leftventricle and the right ventricle at the end of the atrial-ventriculardelay period if a depolarization signal is not detected from the oneventricle during the atrial-ventricular delay period for effecting acoordinated contraction of ventricles contracting in an incoordinatemanner to improve the pumping ability of the heart suffering from heartfailure.
 303. The heart failure treatment device of claim 302, furthercomprising an electrode adapted to be positioned through the coronarysinus to the left ventricle for stimulating the left ventricle.
 304. Theheart failure treatment device of claim 302, wherein the stimulatingcircuit generates pacing pulses for stimulating the left ventricle andthe right ventricle.
 305. The heart failure treatment device of claim302, wherein the stimulation circuit stimulates the left ventriclesubstantially simultaneously with the stimulation of the rightventricle.
 306. The heart failure treatment device of claim 302, whereinthe one ventricle is the right ventricle.
 307. The heart failuretreatment device of claim 302, wherein the one ventricle is the leftventricle.
 308. A method for improving the pumping ability of a heartsuffering from heart failure comprising: positioning a first electrodethrough the coronary sinus to the left ventricle; positioning a secondelectrode in the right ventricle; applying a pacing pulse to the leftventricle through the first electrode; applying a pacing pulse to theright ventricle through the second electrode substantiallysimultaneously with application of the pacing pulse to the leftventricle, wherein the pacing pulses are applied to the left ventricleand the right ventricle at a programmed rate.
 309. The method of claim308, wherein the pacing pulses are applied at the programmed ratewithout regard to any sensing.
 310. A method of improving the pumpingability of a heart suffering from heart failure comprising: sensing fordepolarization signals originating from a first ventricle; andstimulating a second ventricle when a depolarization signal from thefirst ventricle is detected for effecting a coordinate contraction ofventricles contracting in an incoordinate manner to improve the pumpingability of the heart suffering from heart failure.
 311. The method of310, further comprising locating an electrode through the coronary sinusto the left ventricle.
 312. The method of claim 310, wherein the secondventricle is stimulated within a period of time after detecting adepolarization signal from the first ventricle, the period of time beingsufficient to effect a substantially simultaneous contraction of bothventricles.
 313. The method of claim 312, wherein the second ventricleis stimulated within 10 milliseconds after detecting the depolarizationsignal of the first ventricle.
 314. A method of improving the pumpingability of a heart suffering from heart failure comprising: sensing fordepolarization signals originating from a left ventricle; sensing fordepolarization signals originating from a right ventricle; andstimulating the left ventricle and the right ventricle after a timeperiod if a depolarization signal is not detected from either the leftventricle or the right ventricle during the time period for effecting acoordinated contraction of ventricles contracting in an incoordinatemanner to improve the pumping ability of a heart suffering from heartfailure.
 315. A method of improving the pumping ability of a heartsuffering from heart failure comprising: sensing for depolarizationsignals originating from only one ventricle; and stimulating a rightventricle and a left ventricle if a depolarization signal is notdetected from the one ventricle during a time period for effecting acoordinated contraction of ventricles contracting in an incoordinatemanner to improve the pumping ability of a heart suffering from heartfailure.
 316. A method for improving the pumping ability of a heartsuffering from heart failure comprising: sensing for depolarizationsignals origination in an atrium; sensing for depolarization signalsoriginating from a left ventricle; sensing for depolarization signalsoriginating from a right ventricle; and stimulating the left ventricleand the right ventricle after a time period if a depolarization signalis not detected from either the left ventricle or the right ventricleduring the time period for effecting a coordinated contraction ofventricles contracting in an incoordinate manner to improve the pumpingability of a heart suffering from heart failure.
 317. The method ofclaim 316, further comprising stimulating the left ventricle and theright ventricle when a depolarization signal from either the leftventricle or the right ventricle is detected during the time period foreffecting a coordinate contraction of the ventricles.
 318. The method ofclaim 316, wherein the time period is an atrial-ventricular delay. 319.The method of claim 316, wherein the time period is a cardiac cycleinterval.
 320. The method of claim 316, further comprising locating anelectrode through the coronary sinus to the left ventricle.
 321. Themethod of claim 316, wherein stimulating the left ventricle and theright ventricle includes stimulating only one site in the left ventricleand only one site in the right ventricle.
 322. The method of claim 316,wherein stimulating the left ventricle and the right ventricle includesapplying a pacing pulse to the left ventricle and applying a pacingpulse to the right ventricle.
 323. The method of claim 316, whereinstimulating the left ventricle and the right ventricle includesstimulating the left ventricle substantially simultaneously withstimulating the right ventricle.
 324. A method for improving the pumpingability of a heart suffering from heart failure comprising: sensing fordepolarization signals origination in an atrium; sensing fordepolarization signals originating from only one ventricle; andstimulating the left ventricle and the right ventricle after a timeperiod if a depolarization signal is not detected from the one ventricleduring the time period for effecting a coordinated contraction ofventricles contracting in an incoordinate manner to improve the pumpingability of a heart suffering from heart failure.
 325. The method ofclaim 324, further comprising stimulating the left ventricle and theright ventricle when a depolarization signal from the one ventricle isdetected during the time period for effecting a coordinated contractionof the ventricles.
 326. The method of claim 324, wherein the time periodis an atrial-ventricular delay.
 327. The method of claim 324, whereinthe time period is a cardiac cycle interval.
 328. The method of claim324, further comprising locating an electrode through the coronary sinusto the left ventricle.
 329. The method of claim 324, wherein stimulatingthe left ventricle and the right ventricle includes stimulating only onesite in the left ventricle and only one site in the right ventricle.330. The method of claim 324, wherein stimulating the left ventricle andthe right ventricle includes applying a pacing pulse to the leftventricle and applying a pacing pulse to the right ventricle.
 331. Themethod of claim 324, wherein stimulating the left ventricle and theright ventricle includes stimulating the left ventricle substantiallysimultaneously with stimulating the right ventricle.